mem.c

00001 /**
00002  * @file
00003  * Dynamic memory manager
00004  *
00005  * This is a lightweight replacement for the standard C library malloc().
00006  *
00007  * If you want to use the standard C library malloc() instead, define
00008  * MEM_LIBC_MALLOC to 1 in your lwipopts.h
00009  *
00010  * To let mem_malloc() use pools (prevents fragmentation and is much faster than
00011  * a heap but might waste some memory), define MEM_USE_POOLS to 1, define
00012  * MEM_USE_CUSTOM_POOLS to 1 and create a file "lwippools.h" that includes a list
00013  * of pools like this (more pools can be added between _START and _END):
00014  *
00015  * Define three pools with sizes 256, 512, and 1512 bytes
00016  * LWIP_MALLOC_MEMPOOL_START
00017  * LWIP_MALLOC_MEMPOOL(20, 256)
00018  * LWIP_MALLOC_MEMPOOL(10, 512)
00019  * LWIP_MALLOC_MEMPOOL(5, 1512)
00020  * LWIP_MALLOC_MEMPOOL_END
00021  */
00022 
00023 /*
00024  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
00025  * All rights reserved.
00026  *
00027  * Redistribution and use in source and binary forms, with or without modification,
00028  * are permitted provided that the following conditions are met:
00029  *
00030  * 1. Redistributions of source code must retain the above copyright notice,
00031  *    this list of conditions and the following disclaimer.
00032  * 2. Redistributions in binary form must reproduce the above copyright notice,
00033  *    this list of conditions and the following disclaimer in the documentation
00034  *    and/or other materials provided with the distribution.
00035  * 3. The name of the author may not be used to endorse or promote products
00036  *    derived from this software without specific prior written permission.
00037  *
00038  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00039  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00040  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00041  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00042  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00043  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00044  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00045  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00046  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00047  * OF SUCH DAMAGE.
00048  *
00049  * This file is part of the lwIP TCP/IP stack.
00050  *
00051  * Author: Adam Dunkels <adam@sics.se>
00052  *         Simon Goldschmidt
00053  *
00054  */
00055 
00056 #include "lwip/opt.h"
00057 
00058 #if !MEM_LIBC_MALLOC /* don't build if not configured for use in lwipopts.h */
00059 
00060 #include "lwip/def.h"
00061 #include "lwip/mem.h"
00062 #include "lwip/sys.h"
00063 #include "lwip/stats.h"
00064 #include "lwip/err.h"
00065 
00066 #include <string.h>
00067 
00068 #if MEM_USE_POOLS
00069 /* lwIP head implemented with different sized pools */
00070 
00071 /**
00072  * Allocate memory: determine the smallest pool that is big enough
00073  * to contain an element of 'size' and get an element from that pool.
00074  *
00075  * @param size the size in bytes of the memory needed
00076  * @return a pointer to the allocated memory or NULL if the pool is empty
00077  */
00078 void *
00079 mem_malloc(mem_size_t size)
00080 {
00081   struct memp_malloc_helper *element;
00082   memp_t poolnr;
00083   mem_size_t required_size = size + sizeof(struct memp_malloc_helper);
00084 
00085   for (poolnr = MEMP_POOL_FIRST; poolnr <= MEMP_POOL_LAST; poolnr++) {
00086 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00087 again:
00088 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00089     /* is this pool big enough to hold an element of the required size
00090        plus a struct memp_malloc_helper that saves the pool this element came from? */
00091     if (required_size <= memp_sizes[poolnr]) {
00092       break;
00093     }
00094   }
00095   if (poolnr > MEMP_POOL_LAST) {
00096     LWIP_ASSERT("mem_malloc(): no pool is that big!", 0);
00097     return NULL;
00098   }
00099   element = (struct memp_malloc_helper*)memp_malloc(poolnr);
00100   if (element == NULL) {
00101     /* No need to DEBUGF or ASSERT: This error is already
00102        taken care of in memp.c */
00103 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00104     /** Try a bigger pool if this one is empty! */
00105     if (poolnr < MEMP_POOL_LAST) {
00106       poolnr++;
00107       goto again;
00108     }
00109 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00110     return NULL;
00111   }
00112 
00113   /* save the pool number this element came from */
00114   element->poolnr = poolnr;
00115   /* and return a pointer to the memory directly after the struct memp_malloc_helper */
00116   element++;
00117 
00118   return element;
00119 }
00120 
00121 /**
00122  * Free memory previously allocated by mem_malloc. Loads the pool number
00123  * and calls memp_free with that pool number to put the element back into
00124  * its pool
00125  *
00126  * @param rmem the memory element to free
00127  */
00128 void
00129 mem_free(void *rmem)
00130 {
00131   struct memp_malloc_helper *hmem = (struct memp_malloc_helper*)rmem;
00132 
00133   LWIP_ASSERT("rmem != NULL", (rmem != NULL));
00134   LWIP_ASSERT("rmem == MEM_ALIGN(rmem)", (rmem == LWIP_MEM_ALIGN(rmem)));
00135 
00136   /* get the original struct memp_malloc_helper */
00137   hmem--;
00138 
00139   LWIP_ASSERT("hmem != NULL", (hmem != NULL));
00140   LWIP_ASSERT("hmem == MEM_ALIGN(hmem)", (hmem == LWIP_MEM_ALIGN(hmem)));
00141   LWIP_ASSERT("hmem->poolnr < MEMP_MAX", (hmem->poolnr < MEMP_MAX));
00142 
00143   /* and put it in the pool we saved earlier */
00144   memp_free(hmem->poolnr, hmem);
00145 }
00146 
00147 #else /* MEM_USE_POOLS */
00148 /* lwIP replacement for your libc malloc() */
00149 
00150 /**
00151  * The heap is made up as a list of structs of this type.
00152  * This does not have to be aligned since for getting its size,
00153  * we only use the macro SIZEOF_STRUCT_MEM, which automatically alignes.
00154  */
00155 struct mem {
00156   /** index (-> ram[next]) of the next struct */
00157   mem_size_t next;
00158   /** index (-> ram[prev]) of the previous struct */
00159   mem_size_t prev;
00160   /** 1: this area is used; 0: this area is unused */
00161   u8_t used;
00162 };
00163 
00164 /** All allocated blocks will be MIN_SIZE bytes big, at least!
00165  * MIN_SIZE can be overridden to suit your needs. Smaller values save space,
00166  * larger values could prevent too small blocks to fragment the RAM too much. */
00167 #ifndef MIN_SIZE
00168 #define MIN_SIZE             12
00169 #endif /* MIN_SIZE */
00170 /* some alignment macros: we define them here for better source code layout */
00171 #define MIN_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MIN_SIZE)
00172 #define SIZEOF_STRUCT_MEM    LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))
00173 #define MEM_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MEM_SIZE)
00174 
00175 /** If you want to relocate the heap to external memory, simply define
00176  * LWIP_RAM_HEAP_POINTER as a void-pointer to that location.
00177  * If so, make sure the memory at that location is big enough (see below on
00178  * how that space is calculated). */
00179 #ifndef LWIP_RAM_HEAP_POINTER
00180 /** the heap. we need one struct mem at the end and some room for alignment */
00181 u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT] MEM_POSITION;
00182 #define LWIP_RAM_HEAP_POINTER ram_heap
00183 #endif /* LWIP_RAM_HEAP_POINTER */
00184 
00185 /** pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array */
00186 static u8_t *ram;
00187 /** the last entry, always unused! */
00188 static struct mem *ram_end;
00189 /** pointer to the lowest free block, this is used for faster search */
00190 static struct mem *lfree;
00191 
00192 #if (NO_SYS==0) //Pointless if monothreaded app
00193 /** concurrent access protection */
00194 static sys_mutex_t mem_mutex;
00195 #endif
00196 
00197 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00198 
00199 static volatile u8_t mem_free_count;
00200 
00201 /* Allow mem_free from other (e.g. interrupt) context */
00202 #define LWIP_MEM_FREE_DECL_PROTECT()  SYS_ARCH_DECL_PROTECT(lev_free)
00203 #define LWIP_MEM_FREE_PROTECT()       SYS_ARCH_PROTECT(lev_free)
00204 #define LWIP_MEM_FREE_UNPROTECT()     SYS_ARCH_UNPROTECT(lev_free)
00205 #define LWIP_MEM_ALLOC_DECL_PROTECT() SYS_ARCH_DECL_PROTECT(lev_alloc)
00206 #define LWIP_MEM_ALLOC_PROTECT()      SYS_ARCH_PROTECT(lev_alloc)
00207 #define LWIP_MEM_ALLOC_UNPROTECT()    SYS_ARCH_UNPROTECT(lev_alloc)
00208 
00209 #else /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00210 
00211 /* Protect the heap only by using a semaphore */
00212 #define LWIP_MEM_FREE_DECL_PROTECT()
00213 #define LWIP_MEM_FREE_PROTECT()    sys_mutex_lock(&mem_mutex)
00214 #define LWIP_MEM_FREE_UNPROTECT()  sys_mutex_unlock(&mem_mutex)
00215 /* mem_malloc is protected using semaphore AND LWIP_MEM_ALLOC_PROTECT */
00216 #define LWIP_MEM_ALLOC_DECL_PROTECT()
00217 #define LWIP_MEM_ALLOC_PROTECT()
00218 #define LWIP_MEM_ALLOC_UNPROTECT()
00219 
00220 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00221 
00222 
00223 /**
00224  * "Plug holes" by combining adjacent empty struct mems.
00225  * After this function is through, there should not exist
00226  * one empty struct mem pointing to another empty struct mem.
00227  *
00228  * @param mem this points to a struct mem which just has been freed
00229  * @internal this function is only called by mem_free() and mem_trim()
00230  *
00231  * This assumes access to the heap is protected by the calling function
00232  * already.
00233  */
00234 static void
00235 plug_holes(struct mem *mem)
00236 {
00237   struct mem *nmem;
00238   struct mem *pmem;
00239 
00240   LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
00241   LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
00242   LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
00243 
00244   /* plug hole forward */
00245   LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
00246 
00247   nmem = (struct mem *)(void *)&ram[mem->next];
00248   if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
00249     /* if mem->next is unused and not end of ram, combine mem and mem->next */
00250     if (lfree == nmem) {
00251       lfree = mem;
00252     }
00253     mem->next = nmem->next;
00254     ((struct mem *)(void *)&ram[nmem->next])->prev = (mem_size_t)((u8_t *)mem - ram);
00255   }
00256 
00257   /* plug hole backward */
00258   pmem = (struct mem *)(void *)&ram[mem->prev];
00259   if (pmem != mem && pmem->used == 0) {
00260     /* if mem->prev is unused, combine mem and mem->prev */
00261     if (lfree == mem) {
00262       lfree = pmem;
00263     }
00264     pmem->next = mem->next;
00265     ((struct mem *)(void *)&ram[mem->next])->prev = (mem_size_t)((u8_t *)pmem - ram);
00266   }
00267 }
00268 
00269 /**
00270  * Zero the heap and initialize start, end and lowest-free
00271  */
00272 void
00273 mem_init(void)
00274 {
00275   struct mem *mem;
00276 
00277   LWIP_ASSERT("Sanity check alignment",
00278     (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
00279 
00280   /* align the heap */
00281   ram = (u8_t *)LWIP_MEM_ALIGN(LWIP_RAM_HEAP_POINTER);
00282   /* initialize the start of the heap */
00283   mem = (struct mem *)(void *)ram;
00284   mem->next = MEM_SIZE_ALIGNED;
00285   mem->prev = 0;
00286   mem->used = 0;
00287   /* initialize the end of the heap */
00288   ram_end = (struct mem *)(void *)&ram[MEM_SIZE_ALIGNED];
00289   ram_end->used = 1;
00290   ram_end->next = MEM_SIZE_ALIGNED;
00291   ram_end->prev = MEM_SIZE_ALIGNED;
00292 
00293   /* initialize the lowest-free pointer to the start of the heap */
00294   lfree = (struct mem *)(void *)ram;
00295 
00296   MEM_STATS_AVAIL(avail, MEM_SIZE_ALIGNED);
00297 
00298   if(sys_mutex_new(&mem_mutex) != ERR_OK) {
00299     LWIP_ASSERT("failed to create mem_mutex", 0);
00300   }
00301 }
00302 
00303 /**
00304  * Put a struct mem back on the heap
00305  *
00306  * @param rmem is the data portion of a struct mem as returned by a previous
00307  *             call to mem_malloc()
00308  */
00309 void
00310 mem_free(void *rmem)
00311 {
00312   struct mem *mem;
00313   LWIP_MEM_FREE_DECL_PROTECT();
00314 
00315   if (rmem == NULL) {
00316     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("mem_free(p == NULL) was called.\n"));
00317     return;
00318   }
00319   LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
00320 
00321   LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00322     (u8_t *)rmem < (u8_t *)ram_end);
00323 
00324   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00325     SYS_ARCH_DECL_PROTECT(lev);
00326     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_free: illegal memory\n"));
00327     /* protect mem stats from concurrent access */
00328     SYS_ARCH_PROTECT(lev);
00329     MEM_STATS_INC(illegal);
00330     SYS_ARCH_UNPROTECT(lev);
00331     return;
00332   }
00333   /* protect the heap from concurrent access */
00334   LWIP_MEM_FREE_PROTECT();
00335   /* Get the corresponding struct mem ... */
00336   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00337   /* ... which has to be in a used state ... */
00338   LWIP_ASSERT("mem_free: mem->used", mem->used);
00339   /* ... and is now unused. */
00340   mem->used = 0;
00341 
00342   if (mem < lfree) {
00343     /* the newly freed struct is now the lowest */
00344     lfree = mem;
00345   }
00346 
00347   MEM_STATS_DEC_USED(used, mem->next - (mem_size_t)(((u8_t *)mem - ram)));
00348 
00349   /* finally, see if prev or next are free also */
00350   plug_holes(mem);
00351 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00352   mem_free_count = 1;
00353 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00354   LWIP_MEM_FREE_UNPROTECT();
00355 }
00356 
00357 /**
00358  * Shrink memory returned by mem_malloc().
00359  *
00360  * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
00361  * @param newsize required size after shrinking (needs to be smaller than or
00362  *                equal to the previous size)
00363  * @return for compatibility reasons: is always == rmem, at the moment
00364  *         or NULL if newsize is > old size, in which case rmem is NOT touched
00365  *         or freed!
00366  */
00367 void *
00368 mem_trim(void *rmem, mem_size_t newsize)
00369 {
00370   mem_size_t size;
00371   mem_size_t ptr, ptr2;
00372   struct mem *mem, *mem2;
00373   /* use the FREE_PROTECT here: it protects with sem OR SYS_ARCH_PROTECT */
00374   LWIP_MEM_FREE_DECL_PROTECT();
00375 
00376   /* Expand the size of the allocated memory region so that we can
00377      adjust for alignment. */
00378   newsize = LWIP_MEM_ALIGN_SIZE(newsize);
00379 
00380   if(newsize < MIN_SIZE_ALIGNED) {
00381     /* every data block must be at least MIN_SIZE_ALIGNED long */
00382     newsize = MIN_SIZE_ALIGNED;
00383   }
00384 
00385   if (newsize > MEM_SIZE_ALIGNED) {
00386     return NULL;
00387   }
00388 
00389   LWIP_ASSERT("mem_trim: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00390    (u8_t *)rmem < (u8_t *)ram_end);
00391 
00392   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00393     SYS_ARCH_DECL_PROTECT(lev);
00394     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_trim: illegal memory\n"));
00395     /* protect mem stats from concurrent access */
00396     SYS_ARCH_PROTECT(lev);
00397     MEM_STATS_INC(illegal);
00398     SYS_ARCH_UNPROTECT(lev);
00399     return rmem;
00400   }
00401   /* Get the corresponding struct mem ... */
00402   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00403   /* ... and its offset pointer */
00404   ptr = (mem_size_t)((u8_t *)mem - ram);
00405 
00406   size = mem->next - ptr - SIZEOF_STRUCT_MEM;
00407   LWIP_ASSERT("mem_trim can only shrink memory", newsize <= size);
00408   if (newsize > size) {
00409     /* not supported */
00410     return NULL;
00411   }
00412   if (newsize == size) {
00413     /* No change in size, simply return */
00414     return rmem;
00415   }
00416 
00417   /* protect the heap from concurrent access */
00418   LWIP_MEM_FREE_PROTECT();
00419 
00420   mem2 = (struct mem *)(void *)&ram[mem->next];
00421   if(mem2->used == 0) {
00422     /* The next struct is unused, we can simply move it at little */
00423     mem_size_t next;
00424     /* remember the old next pointer */
00425     next = mem2->next;
00426     /* create new struct mem which is moved directly after the shrinked mem */
00427     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00428     if (lfree == mem2) {
00429       lfree = (struct mem *)(void *)&ram[ptr2];
00430     }
00431     mem2 = (struct mem *)(void *)&ram[ptr2];
00432     mem2->used = 0;
00433     /* restore the next pointer */
00434     mem2->next = next;
00435     /* link it back to mem */
00436     mem2->prev = ptr;
00437     /* link mem to it */
00438     mem->next = ptr2;
00439     /* last thing to restore linked list: as we have moved mem2,
00440      * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
00441      * the end of the heap */
00442     if (mem2->next != MEM_SIZE_ALIGNED) {
00443       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00444     }
00445     MEM_STATS_DEC_USED(used, (size - newsize));
00446     /* no need to plug holes, we've already done that */
00447   } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
00448     /* Next struct is used but there's room for another struct mem with
00449      * at least MIN_SIZE_ALIGNED of data.
00450      * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
00451      * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
00452      * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00453      *       region that couldn't hold data, but when mem->next gets freed,
00454      *       the 2 regions would be combined, resulting in more free memory */
00455     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00456     mem2 = (struct mem *)(void *)&ram[ptr2];
00457     if (mem2 < lfree) {
00458       lfree = mem2;
00459     }
00460     mem2->used = 0;
00461     mem2->next = mem->next;
00462     mem2->prev = ptr;
00463     mem->next = ptr2;
00464     if (mem2->next != MEM_SIZE_ALIGNED) {
00465       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00466     }
00467     MEM_STATS_DEC_USED(used, (size - newsize));
00468     /* the original mem->next is used, so no need to plug holes! */
00469   }
00470   /* else {
00471     next struct mem is used but size between mem and mem2 is not big enough
00472     to create another struct mem
00473     -> don't do anyhting. 
00474     -> the remaining space stays unused since it is too small
00475   } */
00476 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00477   mem_free_count = 1;
00478 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00479   LWIP_MEM_FREE_UNPROTECT();
00480   return rmem;
00481 }
00482 
00483 /**
00484  * Adam's mem_malloc() plus solution for bug #17922
00485  * Allocate a block of memory with a minimum of 'size' bytes.
00486  *
00487  * @param size is the minimum size of the requested block in bytes.
00488  * @return pointer to allocated memory or NULL if no free memory was found.
00489  *
00490  * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
00491  */
00492 void *
00493 mem_malloc(mem_size_t size)
00494 {
00495   mem_size_t ptr, ptr2;
00496   struct mem *mem, *mem2;
00497 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00498   u8_t local_mem_free_count = 0;
00499 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00500   LWIP_MEM_ALLOC_DECL_PROTECT();
00501 
00502   if (size == 0) {
00503     return NULL;
00504   }
00505 
00506   /* Expand the size of the allocated memory region so that we can
00507      adjust for alignment. */
00508   size = LWIP_MEM_ALIGN_SIZE(size);
00509 
00510   if(size < MIN_SIZE_ALIGNED) {
00511     /* every data block must be at least MIN_SIZE_ALIGNED long */
00512     size = MIN_SIZE_ALIGNED;
00513   }
00514 
00515   if (size > MEM_SIZE_ALIGNED) {
00516     return NULL;
00517   }
00518 
00519   /* protect the heap from concurrent access */
00520   sys_mutex_lock(&mem_mutex);
00521   LWIP_MEM_ALLOC_PROTECT();
00522 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00523   /* run as long as a mem_free disturbed mem_malloc */
00524   do {
00525     local_mem_free_count = 0;
00526 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00527 
00528     /* Scan through the heap searching for a free block that is big enough,
00529      * beginning with the lowest free block.
00530      */
00531     for (ptr = (mem_size_t)((u8_t *)lfree - ram); ptr < MEM_SIZE_ALIGNED - size;
00532          ptr = ((struct mem *)(void *)&ram[ptr])->next) {
00533       mem = (struct mem *)(void *)&ram[ptr];
00534 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00535       mem_free_count = 0;
00536       LWIP_MEM_ALLOC_UNPROTECT();
00537       /* allow mem_free to run */
00538       LWIP_MEM_ALLOC_PROTECT();
00539       if (mem_free_count != 0) {
00540         local_mem_free_count = mem_free_count;
00541       }
00542       mem_free_count = 0;
00543 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00544 
00545       if ((!mem->used) &&
00546           (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
00547         /* mem is not used and at least perfect fit is possible:
00548          * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */
00549 
00550         if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
00551           /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
00552            * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
00553            * -> split large block, create empty remainder,
00554            * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
00555            * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
00556            * struct mem would fit in but no data between mem2 and mem2->next
00557            * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00558            *       region that couldn't hold data, but when mem->next gets freed,
00559            *       the 2 regions would be combined, resulting in more free memory
00560            */
00561           ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
00562           /* create mem2 struct */
00563           mem2 = (struct mem *)(void *)&ram[ptr2];
00564           mem2->used = 0;
00565           mem2->next = mem->next;
00566           mem2->prev = ptr;
00567           /* and insert it between mem and mem->next */
00568           mem->next = ptr2;
00569           mem->used = 1;
00570 
00571           if (mem2->next != MEM_SIZE_ALIGNED) {
00572             ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00573           }
00574           MEM_STATS_INC_USED(used, (size + SIZEOF_STRUCT_MEM));
00575         } else {
00576           /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
00577            * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
00578            * take care of this).
00579            * -> near fit or excact fit: do not split, no mem2 creation
00580            * also can't move mem->next directly behind mem, since mem->next
00581            * will always be used at this point!
00582            */
00583           mem->used = 1;
00584           MEM_STATS_INC_USED(used, mem->next - (mem_size_t)((u8_t *)mem - ram));
00585         }
00586 
00587         if (mem == lfree) {
00588           /* Find next free block after mem and update lowest free pointer */
00589           while (lfree->used && lfree != ram_end) {
00590             LWIP_MEM_ALLOC_UNPROTECT();
00591             /* prevent high interrupt latency... */
00592             LWIP_MEM_ALLOC_PROTECT();
00593             lfree = (struct mem *)(void *)&ram[lfree->next];
00594           }
00595           LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
00596         }
00597         LWIP_MEM_ALLOC_UNPROTECT();
00598         sys_mutex_unlock(&mem_mutex);
00599         LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
00600          (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
00601         LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
00602          ((mem_ptr_t)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
00603         LWIP_ASSERT("mem_malloc: sanity check alignment",
00604           (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
00605 
00606         return (u8_t *)mem + SIZEOF_STRUCT_MEM;
00607       }
00608     }
00609 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00610     /* if we got interrupted by a mem_free, try again */
00611   } while(local_mem_free_count != 0);
00612 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00613   LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
00614   MEM_STATS_INC(err);
00615   LWIP_MEM_ALLOC_UNPROTECT();
00616   sys_mutex_unlock(&mem_mutex);
00617   return NULL;
00618 }
00619 
00620 #endif /* MEM_USE_POOLS */
00621 /**
00622  * Contiguously allocates enough space for count objects that are size bytes
00623  * of memory each and returns a pointer to the allocated memory.
00624  *
00625  * The allocated memory is filled with bytes of value zero.
00626  *
00627  * @param count number of objects to allocate
00628  * @param size size of the objects to allocate
00629  * @return pointer to allocated memory / NULL pointer if there is an error
00630  */
00631 void *mem_calloc(mem_size_t count, mem_size_t size)
00632 {
00633   void *p;
00634 
00635   /* allocate 'count' objects of size 'size' */
00636   p = mem_malloc(count * size);
00637   if (p) {
00638     /* zero the memory */
00639     memset(p, 0, count * size);
00640   }
00641   return p;
00642 }
00643 
00644 #endif /* !MEM_LIBC_MALLOC */